2022/11/01 by Tong Su, Su, Tong, Ching Hua Lee +13
Materials Science · #2D Materials and Applications #Applied Physics (physics.app-ph) #FOS: Physical sciences #Materials Science (cond-mat.mtrl-sci) #Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
paper · pdf · doi:10.48550/arxiv.2211.00560
openalex publication_date 2022/11/01 · openalex created_date 2022/11/07 · openalex updated_date 2026/07/28
Two-dimensional (2D) niobium oxydihalide NbOI2 has been recently demonstrated as an excellent in-plane piezoelectric and nonlinear optical materials. Here we show that Janus niobium oxydihalide, NbOXY (X, Y = Cl, Br, I and X≠Y), is a multifunctional anisotropic semiconductor family with exceptional piezoelectric, electronic, photocatalytic and optical properties. NbOXY are stable and mechancially flexible monolayers with band gap around the visible light regime of ∼ 1.9 eV. The anisotropic carrier mobility of NbOXY lies in the range of 103 ∼ 104 cm2V-1s-1, which represents some of the highest among 2D semiconductors of bandgap \gtrsim 2 eV. Inversion symmetry breaking in Janus NbOXY generates sizable out-of-plane d31 piezoelectric response while still retaining a strong in-plane piezoelectricity. Remarkably, NbOXY exhibits an additional out-of-plane piezoelectric response, d32 as large as 0.55 pm/V. G0W0-BSE calculation further reveals the strong linear optical dichroism of NbOXY in the visible-to-ultraviolet regime. The optical absorption peaks with 14∼18 % in the deep UV regime (5∼6 eV), outperforming the vast majority of other 2D materials. The high carrier mobility, strong optical absorption, sizable built-in electric field and band alignment compatible with overall water splitting further suggest the strengths of NbOXY in energy conversion application. We further propose a directional stress sensing device to demonstrate how the out-of-plane piezoelectricity can be harnessed for functional device applications. Our findings unveil NbOXY as an exceptional multifunctional 2D semiconductor for flexible electronics, optoelectronics, UV photonics, piezoelectric and sustainable energy applications.